Plugs keep on throwing error

[freakazoid]

In Feb when the gearbox was replaced, BMW also replaced the spark plugs due to a slight misfire when idling (cold and hot).

Misfire was gone for a while and came back about two weeks ago to the point where there is a slight hesitation when accelerating mildly. When the car is started from cold and left idling it will idle at a higher rev for a while and then shake a bit and drop immediately to normal revs. This is when the misfire is most pronounced. When normal operating temp is reached and I idle for a while in traffic or robot the misfire while appear. It seems as if it is on one cylinder as the time between misfire seems constant.

Car went in yesterday and after two days of diagnosis, plugs were again identified as the problem.

I was not happy with this result and the technician insists that the plugs came up as the issue in their diagnosis. Raised the issue with the Workshop manager and after seeing the claim for plugs in Feb told the technies to re-diagnose.

So my question is, can something else be causing the plugs to throw an error or possibly damage the plugs? Are the coilpacks perhaps the culprits? Injectors?

Getting a bit scared of the car as in addition to the idling issue, diff is being replaced, new door locks and one rear brake disc was cracked.

 

[Kish2604]

is this car under motorplan?

99% is that your issue revolves around a leaky injector... have seen it with other cars and my own, the best method of tracing the bad one is by letting the car sit overnight and pull the plugs the next morning, the one that is wet is your culprit...

 

[freakazoid]

is this car under motorplan?

99% is that your issue revolves around a leaky injector... have seen it with other cars and my own, the best method of tracing the bad one is by letting the car sit overnight and pull the plugs the next morning, the one that is wet is your culprit...

Motorplan expires in two weeks time.

I think you are correct. Sometimes there is a smell of petrol when starting in the mornings.

 

[Major]

Yeah spark plugs can't throw an error, on the 335i it's an inferred error because it's running rich, so your options are too much fuel or too little spark. ISIS doesn't diagnose faulty coils/injectors well or at all.

• Ask them if there's an outstanding replacement due for your injectors, lots of 335i's had all of their injectors replaced as part of a campaign.
• They can test spark/coil combos by 'flipping' the coils around (coil 1 to cylinder 3, coil 2 to cylinder 4, etc) and see if the car magically reports a new cylinder at fault
• They can do the above with fuel injectors as well

Considering it went away and came back, I suspect injector, as the spark plug that was clean has now got buildup from excess fuel and has the same issue.

 

[Kish2604]

nicely explained Major....

OP... u have PM

 

[Twinz]

Bmw Dealerships are just plain hopeless. :thumbdo:

 

[freakazoid]

Bmw said they will pull the injectors to see if they the cause while they waiting for the diff to arrive ( at a cost of R27 700 to MP)

 

[Major]

Dealerships love getting MP approvals, so milk them while you can.

 

[Philip Foglar]

They can swap the plugs, coils, and injectors around to find the culprit - you would think they would "know" this themselves... :nonono:

 

[sclass]

Bmw said they will pull the injectors to see if they the cause while they waiting for the diff to arrive ( at a cost of R27 700 to MP)

Wait, twenty seven grand for a diff...............?! How much is a Quaife LSD...??

Why a new diff though? Sorry for going off topic